Jacquleine,
I would NOT use IDM, but use the built in Source Code policy. It works pretty well across the board.
I would update some of the policy to get rid of False Positives.
Update the VB rule: Attribute\sVB_Name\s=\s"(?!Sheet|Module|This|Chart|User|Content)
Add the exception for MS Excel Macro
PLEASE MARKED SOLVED WHEN POSSIBLE
Good Luck
Ronak